Getting the following error message when trying to reply to a specific email address. This person contacted me through a craigslist ad, I responded and we emailed back and forth several times, however randomly yesterday I got the following error message when trying to reply.
Error 550 5.1.1 bad mailbox name. Open the message and Send to try again.
I've tried creating a new message, restarting the app, nothing is working. He has sent me multiple emails since but I can't reply to any of them.
Any idea why this might be happening?